The role of an aromatic group in remote chiral induction during conjugate addition of alpha-sulfonylallylic carbanions to ethyl crotonate.
The impact of a remote aromatic nucleus on the stereochemical outcome of the conjugate addition of alpha-sulfonylallylic carbanions to an alpha,beta-unsaturated ester was investigated. alpha-Regioselectivity coupled with anti-diastereoselectivity is accompanied by a prominent preference for relative configuration 3 over 4. The 9-anthryl moiety has shown itself greatly superior over all other groups in this bias. A lithium ion-aromatic pi interaction has been postulated as decisive for the remote transmission of chirality.
Levinger
Shlomo
S
Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel.
Nair
Ranjeet
R
Hassner
Alfred
A